1. Field of the Invention
The present invention relates to an optical module for use in transmitting and receiving optical signals in an optical system, and also relates to an optical element of the optical module.
2. Description of the Related Art
FIG. 16 is a sectional view showing the configuration of a conventional optical module as disclosed in the Patent Application Laid-Open No. 11-26783. In the figure, reference numeral 101 denotes an optical fiber, 102 denotes a light detecting element for detecting the total reflected light reflected by the tip end of the optical fiber, which end is cut in an oblique manner, and carrying out a light-to-electricity conversion, 103 denotes a step-form stopper for setting the position of the optical fiber 101 by abutting it against the tip end portion of the optical fiber, and 104 denotes an optical fiber suppressor.
FIG. 17 is a plan view showing a silicon substrate of the conventional optical module. In the figure, reference numeral 105 denotes a silicon substrate, 106 denotes a guide groove for fixing the optical fiber therein, 107 denote a pair of substrate-side alignment patterns disposed symmetrically the guide groove 106, each pattern being part of a metalized pattern, and numeral 108 denote AuSn solder for fixing the light detecting element 102 to the silicon substrate in the final process.
FIG. 18 is a plan view showing the front surface and the rear surface of the light detecting element 102 of the above-explained optical module. In the figure, reference numeral 109 denotes an electrode formed on the front surface side, 110 denotes an incident-light incident window formed in the rear surface side for receiving the incident signal light, 111 denotes a light incident surface, and numeral 112 denote a pair of light detecting element side alignment patterns disposed symmetrically about the light receiving surface 111, each being formed as a part of a metalized pattern.
Next, the operation for firmly connecting the light detecting element to the silicon substrate in the conventional optical module is explained.
FIG. 19 is an illustration showing the configuration of a visual alignment execution system for firmly connecting the light detecting element to the silicon substrate. In the figure, reference numeral 113 denotes an arm for holding the light detecting element 102 and adjusting the position thereof, numeral 114 denotes infrared rays upwardly irradiated from the lower side thereof, numeral 115 denotes a camera for taking photographs by use of the infrared rays, and 116 denotes a heater for heating and melting the solder when the desired relative positions between the optical element and the silicon substrate are obtained. During the positional adjustment process, the position of the light detecting element 102 is first adjusted by driving the arm 113, and thereafter the arm is fixed when the center of each of the alignment patterns 107 of the silicon substrate 105 and that of each of the alignment patterns 112 of the light detecting element 102 are aligned. After these operations, the heater 116 is heated to melt the AuSn solder 108 provided on the silicon substrate 105, so as to firmly attach the light detecting element 102 to the silicon substrate 105.
It should be noted that the above conventional technique has been explained as to the case in which a light detecting element is employed as the optical element. However, the same positional adjustment process is used as well for firmly attaching a laser diode (hereinafter may be referred to just as an xe2x80x9cLDxe2x80x9d), an optical waveguide and so on to the silicon substrate.
Since the conventional optical module is constructed as explained above, the operating section of the optical element side provided as the light incident surface of a light detecting element, the light emitting point of a laser diode and so on are formed by a different process from the process for forming the optical-element-side alignment patterns, each provided as a metal mark by use of different masks. On the other hand, the V-shape guide groove in which a unidirectional optical fiber is to be mounted and the substrate-side alignment patterns each provided as a metal mark are processed also differently by using different masks. Due to these different processes by use of different masks, there has been produced a discrepancy of several micrometers therebetween, so that no matter how precisely the optical element, the optical fiber and so on are mounted, there has been caused a discrepancy between the operating section of the optical element side such as the light incident surface, and the light emitting point and the core of the optical fiber, which should essentially be matched precisely, so that a dispersion in the coupling efficiency among each of the optical modules has been caused, thereby to lowering the yield of the thus manufactured optical modules as a whole.
The present invention has been proposed to solve the problems aforementioned, and it is an object of the present invention to provide an optical module capable of improving the coupling efficiency between an optical element and a substrate for receiving the optical element by raising the precision in the relative positional alignments and thereby raising the yield of the optical modules as a whole, and also an optical element as an important element configuring the optical module.
In order to achieve the above objects, the optical module according to a first aspect of the present invention is composed essentially of an optical element and a substrate firmly connected to each other, wherein the optical element is formed with one or more than one metal marks for the positional alignment with the substrate, and the substrate is formed with an optical member mounting section and one or more than one etching marks for alignment with the optical element, the recessed etched marks being formed by a process in which the same mask as that used for forming the optical member mounting section is used.
In this configuration, the metal masks are formed in a protruded manner form the surface of the optical element, and the recessed etched marks are formed in a receding manner from the surface of the substrate.
The optical module according to another aspect of the present invention is composed of an optical element and a substrate firmly connected to each other, wherein the optical element is formed with an operating section, an optical-element-side electrode and one or more than one guide sections for the positional alignment with the substrate, and the substrate is formed with an optical member mounting section and one or more than one etching marks for alignment with the optical element, wherein the guide sections are formed by a process in which the same mask as that used for forming the operating section is used, and the recessed etched marks are formed by a process in which the same mask as that used for forming the optical member mounting section is used.
In the above construction, the optical element further comprises position sensing metals each provided on the lateral end portion of the optical element, each of the position sensing metals having a position sensing section whose position is adjusted by the guide section.
The optical module according to another aspect of the present invention is configured in such a manner that the substrate is formed with a recess for accommodating a substrate-side electrode and solder mounted on the electrode, wherein the optical-element-side electrode is not brought into contact with the substrate even when the optical element is disposed at the connecting position to the substrate, and the position sensing metals are abutted against the surface of the substrate formed with a plurality of etching marks.
The optical module according to another aspect of the present invention is configured in such a manner that the substrate is formed with a recess for accommodating a substrate-side electrode and solder mounted on the electrode, wherein the optical-element-side electrode is not brought into contact with the substrate even when the optical element is disposed at the connecting position to the substrate, and the position guide sections are abutted against the surface of the substrate formed with a plurality of recessed etched marks.
The optical element according to still further aspect of the present invention is constructed such that it comprises an operating section and one or more than one guide sections for the positional alignment with a substrate to which the optical element is to be firmly connected, wherein the guide sections are formed by a process in which the same mask as that used for forming the operating section is used.
The optical element as constructed above according to yet still further aspect of the present invention further comprises one or more than one position sensing metals each provided on the lateral end portion of the optical element, each of the position sensing metals having a position sensing section whose position is adjusted by the guide section.